1. Field of the Invention
The present invention relates generally to seals and structures used to effect a fluid seal between multiple mechanical or structural elements and, more particularly, to composite seals and structures used to effect fluid seals between mechanical or structural elements which may be relatively movable with respect to one another wherein the seal is effective in both low and high pressure applications.
2. State of the Art
Seals are conventionally used to maintain a substance, such as a fluid or gas, located in one area or zone from escaping to another area or zone while allowing relative movement of two or more mechanical components with one of the mechanical components traversing through both areas or zones. Such seals may also be used in keeping contaminants, such as dirt, dust or other particulate-type materials, from entering into a specified area or zone. For example, it may be desirable to maintain a lubricant in a specified area or zone while keeping dust or other particulates from entering into the same zone and contaminating the lubricant.
As will be appreciated by those of ordinary skill in the art, the ability to maintain adequate lubrication between two relatively movable machine components, as well as the ability to limit contaminants from entering between the two relatively movable machine components, greatly enhances the working efficiency of the machine components and also greatly reduces wear of such components, thereby increasing the usable life thereof. Additionally, the ability to keep a fluid within a specified zone, sometimes while exhibiting elevated pressures relative to other areas adjacent the zone, may be essential to the proper operation of the machine, device or structure in which the seal is disposed.
One common example of mechanical components that move with respect to one another is a piston and bore (which may also be referred to as a rod and cylinder). For instance, a piston may have an outer surface that is complementary and generally coaxial with the inner surface of a bore in which the piston moves axially, with or without rotation. It is usually desirable that no fluid flow around the piston, so that pressure within the bore may cause the piston to move. Moreover it is also preferred that the piston remain relatively centered within the bore, to prevent the surfaces of the piston and the bore from contacting one another.
Seals take various forms and are made of numerous types of materials depending on their intended service and anticipated working environment. O-rings are an example of a simple type of seal. Another type of seal conventionally used in conjunction with two or more relatively moving machine components are lip seals. Generally, lip seals exhibit a more complex cross-sectional geometry than o-rings and are correspondingly more complex to manufacture. O-rings and lip seals are relatively simple in their installation and operation as will be appreciated by those of ordinary skill in the art.
Another type of available seal may be referred to as a composite seal. Examples of composite seals are described in U.S. Pat. No. 3,848,880, issued to Tanner, and U.S. Pat. No. 4,635,945, issued to Beck, the disclosures of each of which patents are incorporated by reference herein in their entireties. Generally, composite seals include two or more seal elements or components that cooperatively and interdependently define and maintain the separation of multiple zones or areas such as discussed hereinabove. The two different seal elements may include two substantially annular, or ring-like, members formed of different materials so as to take advantage of the different sealing or other structural characteristics offered by such different materials. For example, one of the seal elements may be formed of a first specified material and configured to provide an efficient seal at relatively low pressures while another of the seal elements may be configured of a substantially different material and configured to provide an efficient seal when subject to elevated pressures.
Sometimes composite seals may be configured such that a portion of one seal element cooperatively engages and interlocks with a portion of another seal element such as described with the aforementioned Tanner and Beck patents. However, such cooperative and interlocking structures are often difficult to properly assemble. Moreover, composite seals will oftentimes become separated during installation between, for example, two relatively movable machine elements requiring removal and reassembly of the seal elements.
For example, referring to FIG. 1, a cross section of a composite seal 10 is shown that is generally similar to that described by the Beck patent. The seal 10 includes a first seal element 12 and a second seal element 14. The second seal element 14 exhibits a cross-sectional geometry that defines a throat 16 and a recess 18 that is radially enlarged relative to the throat 16. The first seal element 12 includes a protrusion 20 that exhibits a cross-sectional geometry that is complementary to the recess 18 of the second seal element 14. Adjacent the throat 16 is a pair of angled surfaces 22 which define an angle θ1 that is approximately 60° as such angled surfaces 22 extend toward the throat 16. On the opposite side of the throat 16 is a pair of angled surfaces 24 which define an angle θ2 that is approximately 40° as the angled surfaces 24 extend away from the throat 16. The first seal element 12 includes surfaces that complementarily mate with the angled surfaces 22 and 24 of the second seal element 14.
While the geometric configuration of the seal 10 may provide a relatively effective interlock between the first seal element 12 and the second seal element 14 (i.e., by way of the enlarged recess 18 as compared to the throat 16 and the cooperatively mating protrusion 20), the same configuration has made it difficult to assemble (or reassemble) the first and second seal elements 12 and 14. For example, the radially enlarged portions of the protrusion 20 (i.e., the portion configured to matingly engage the recess 18) may not become entirely inserted or installed within the recess 18 as intended. Rather, one of the radially extending edges of the protrusion 20 may get caught on an edge of the throat 16 and not become entirely disposed within the recess 18. In another example, air may become trapped between the protrusion 20 and the recess 18 such that the first seal element 12 is not entirely seated within second seal element 14 as intended. The partial seating of one component relative to the other can have a deleterious effect on the performance of the composite seal 10.
It is, therefore, desirable to provide a composite seal which provides effective sealing between multiple machine elements under varying conditions which is also simple to manufacture, assemble and install.